Eric Rescorla wrote:
> At Fri, 8 Aug 2008 17:31:15 +0100,> Dave Korn wrote:>
>> Eric Rescorla wrote on 08 August 2008 16:06:
>>
>>
>>> At Fri, 8 Aug 2008 11:50:59 +0100,
>>> Ben Laurie wrote:
>>>
>>>> However, since the CRLs will almost certainly not be checked, this
>>>> means the site will still be vulnerable to attack for the lifetime of
>>>> the certificate (and perhaps beyond, depending on user
>>>> behaviour). Note that shutting down the site DOES NOT prevent the attack.
>>>>
>>>> Therefore mitigation falls to other parties.
>>>>
>>>> 1. Browsers must check CRLs by default.
>>>>
>>> Isn't this a good argument for blacklisting the keys on the client
>>> side?
>>>
>> Isn't that exactly what "Browsers must check CRLs" means in this context
>> anyway? What alternative client-side blacklisting mechanism do you suggest?
>>
>
> It's easy to compute all the public keys that will be generated> by the broken PRNG. The clients could embed that list and refuse> to accept any certificate containing one of them. So, this> is distinct from CRLs in that it doesn't require knowing > which servers have which cert...

Funnily enough I was just working on this -- and found that we'd end up
adding a couple megabytes to every browser. #DEFINE NONSTARTER. I am
curious about the feasibility of a large bloom filter that fails back to
online checking though. This has side effects but perhaps they can be
made statistically very unlikely, without blowing out the size of a browser.

Updating the filter could then be something we do on a 24 hour
autoupdate basis. Doing either this, or doing revocation checking over
DNS (seriously), is not necessarily a bad idea. We need to do better
than we've been.